Alcohol recovery process



Patented Jan. 25, 1944 Awonor. ancovmr nocass Henry 0. Hotter-n, Hillside, N.

mesne assignments, to 8 pany, Linden, N. 1.,

by tamlard Alcohol Coma corporation a! Delaware 'No Drawing. Application January 1 Serial No. 425,349

2 Claims. '(Cl. 202-51) The present invention relatesto a process for the recovery of alcohols from dilute acid extracts,

particularly those dilute acid extracts which are obtained as a residue from a prior process-in which alkyl acid esters are hydrolyzed and distilled to yield olefin hydration products.

Olefin hydration processes, in brief, consist in the absorption of olefin in 60-98% sulfuric acid, or phosphoric acid, which forms an extract of alkyl acid esters. then diluted with water to an acid concentration of 35-50% acidstrength on an olefin-free basis, hydrolyzed and steam strlppedto recover alcohol. Such a process is particularly applicable to the manufacture ofsecondaryaliphatic alcohols although it is also used for preparing tertiary alcohols. The residue from the distillation step is a weak acid, commonly designated as slop acid, which contains from 0.5% to 5% ona volume basis of unrecovered olefin in the form of alcohols and an acid concentration of from 35-50% on an alcohol-free basis. In the ordinaryoperation of an olefinhydrbtion plant, this slop acid is then put through a recovery process in which it is first concentrated to an acid concentration of from 88-93% strength and then oxidized or bleached after which it is incondition for recycle to the olefin hydration process proper. covery process contains no provision for the recovery of the residual olefin -in the i'orm of alcohol so it is therefore lost during the. acid recovery step. Where the olefin hydration product obtained is an alcohol, the quantity of alcohol lost in the slop acid represents about 1-5% of the total alcohol produced. Since a moderately large commercial olefin hydration plant produces from three to five million gallons ofslop acid per year, it is readily apparent that the loss of olefin as l oh l d rin he acid recovery process is enormous.

The principal object of the present invention is the recovery of 5% to 5% by volume of alcohol from the dilute or weak acid recovered from the steam distillation either as alcohol or its corresponding olefin which can b recycled to the absorption and hydrolyzing steps thereby increasing the overall yield of alcohol based upon olefin absorbed. This and other objects of this invention will be apparent to those skilled in the art upon reading the following description. The a1- coholic solution obtained as' a result of the operation of the process of the present invention may be used as such for the dilution ofconcentrated extracts in which the olefin corresponding to the alcohol has been absorbed or concentrated for use in any purpose to which alcohols are customarily applied.

According to the present invention, residual acid extracts or slop acids of sulfuric or phosphoric acid, such as those obtained from an alcohol re- The concentrated extract is the alcohols may be drated to alcohols. are

' tained within.

olefins-have been hyheated to a temperature of from 200-400 F. under the pressure developed at these temperatures which ranges from to 125 lbsJsq. in. for a period offrom, 1-3 hours of batch operation. The time of heating is dependent to a large extent upon the temperature mainthe pressure still. The lower temperatures and pressures require a longer period of heating and conversely the higher temperatures and pressures cause the liberation of the'products in a shorter period oi time. Alcohol and some regenerated olefin is taken overhead under pressure. After the alcohol and olefin have been removed, the residual acid is then ready for processing in the ordinary recovery plant. The olefin recovered is used to enrich the feed to an olefin absorber and the alcoholic distillate is either redlstilled to obtain concentrated alcohol or used without further processing to dilute rich concentrated acid extracts. This is of a decided advantage because in the hydration of olefin by the covery process in which absorption-in-acid method th primary object is to maintain The acid reas high an olefin-acid ratio as possible. The dilute aqueous alcohol solution can be used for dilution of the strong acid extract thereby making up the usual loss of alcohol in the weak acid recovered from the steam distillation. The

process of this invention maybe made continuous by adjusting the feed of slop acid to the pressure still to balance the total of the products taken overhead as distillates and the completely stripped acid removed from the pressure still. The aqueous alcoholic distillate recovered is equivalent in amount to about 5% to 12% volulne of the slop acid charged'to the pressure still. The amount of olefin recovered either as olefin or alcohol ranges from -99% of the olefin, in the form of alcohol. present in the slop acid charged to the pressure still.

The process is operated continuously by adjusting the acid feed to the rate of recovery of alcohol and its corresponding olefin. The range of temperature and pressure used for continuous distillation is the same as for batch operation, 1. e. 25-125 lbs/sq. in. at 200-400 F. The iced-rate is ad- J'usted to allow for a distillation time of l to 3 hours, preferably about 1 /2 hours at 300-350 F.

The following examples are given for the-purpose of illustrating the inventio Example 1 873.5 lbs. of slop acid containing 46% sulfuric acid on an alcohol-free basis, containing 0.4% by volume alcohol was charged to a pressure still, heated to 350 F. for a period of three hours. The maximum pressure attained at this temperature was 55-65 lbs/sq. in. 1.125 lbs. of butene in the form of gas wa obtained, together with 85.5 lbs. or aqueous distillate containing 0.313 1b. sure vessel to a temperature of from 200-400 of alcohol. F. under the pressure developed at these tem- Example 2 peratures for a period of from 1 to 3 hours, 842 I of slop acid containing 44% sulfuric while taking alcohol and olefin off overhead under acid on an alcohol-free basis and .88 weight per- 5 pressure and condensing the alcohol' cent alcohol, was charged to a pressure still and A 9 for the recovery of 84601101 distilled at 5 under a pressure of dilute solutions of alkyl sulfates in slop acid of for three hours 4.92 lbs of C4 gas irom 35-50% acid concentration on an alcoholwas t n together with 26 of aqueous free basis and containing only sufficient allgvl sultillate containing .816 lb. of butyl alcohol. fate capable of yieldms not over 5% of alcohol, What is claim d i which comprises heating the slop acid in a pres- 1. The process for the recovery of alcohol from sure Vessel a p u 'e f from 2 00 4 00 F. dilute acid solutions of alkyl sulfates in slop acid under a Pressure of from 25 t 125 l s-/ qln. f r

of from 35-50% acid concentration on an alcohola e d of from 1 to 3 hours, while taking 1- free basis and containing only sufficient alkyl sul- 15 who! and olefin ofi overhead under pressure and fate capable of yielding not over 5% of alcohol, condensmg th al hol.

which comprises heating the slop acid in a pres- HENRY '0. MOTTERN. 

